Alcubierre Drive antimatter requirements

Some sources say, that alcubierre warp drive would have no need for exotic matter but to create a warp bubble around a shuttle-sized spaceship would require only 100-500 kg of antimatter. Still some believe it would not function without exotic matter and some positive energy. The question is: Is it possible to use antimatter for warp fuel and for how long? It is quite pointless if you could only warp the space for a second.